Roller bearings are known that include a first side ring, a second side ring and a plurality of bridges extending in an axial direction so as to connect the side rings. A pocket for retaining a roller body is defined between each two adjacent bridges and the side rings. The two side rings and the bridges may be integrally formed, thereby providing a solid cage manufactured in one-piece.
In order to manufacture such a solid cage, the retaining pockets for the roller bodies may be milled or cut out of a ring-shaped blank using a milling cutter. The blank may be comprised of brass or bronze. Such cages advantageously provide a stable construction. In addition, it is also possible to manufacture such a solid cage from a plastic material using an injection molding process.
The applications for roller bearings having a solid cage are diverse. In particular, however, it is noted that such cages are often used in railroad engineering, such as in a traction motor for driving the locomotive. In such applications, a cylindrical roller bearing that includes the above-described cage is often utilized for rotatably supporting the pinion.
However, because the roller bearing cage may be subjected to relatively large loads in the traction motor, the cage sometimes breaks during operation of the locomotive. Breakage of the cage could cause a blockage or jamming of the roller bearing and thus blockage or stoppage of the traction motor.
For a locomotive in one-track train operation, such a breakage could cause a blockage of the railway track for several hours, in certain circumstances even several days. Therefore, in particular for bearings utilized in traction motors for locomotives, it is known to utilize riveted cages that are provided with so-called Huck bolt rivets. In such embodiments, instead of a one-piece cage, a cage comprised of a plurality of parts that are riveted together is used. More specifically, the side rings and the bridges are riveted together, rather than being integrally formed.
A cage breakage can be ascertained in the train driver's cabin based upon a change in operating performance, e.g., increased power consumption. When a cage breakage is determined, the driver can attempt to continue to drive to the next passing loop or to the next train station, so as to avoid blocking the track. Huck bolt riveting typically prevents a cage breakage from causing a blockage of the roller bearing that could disable the locomotive and require repair on the spot.
However, such cages riveted with Huck bolts exhibit a lower structural strength than a one-piece cage. As a result, such cages are less resistant to mechanical loading and thus are more susceptible to breakage under heavy loads, even though such cages have good fail-safe properties.